Plurality of imaging optical systems and image pickup apparatus using the same

ABSTRACT

A plurality of imaging optical systems includes at least two imaging optical systems having different focal lengths. Each imaging optical system includes in order from an object side, a front lens unit having a positive refractive power, a diaphragm member, a focusing lens unit having a negative refractive power, and a rear lens unit. The front lens unit includes one of a positive lens and a negative lens as a common lens, and each of at least two imaging optical systems from among the plurality of imaging optical systems includes at least one common lens. At the time of focusing, only the focusing lens unit moves on an optical axis. Each imaging optical system satisfies the following conditional expression (1), and the plurality of imaging optical systems satisfy the following conditional expression (2). 
       0.06&lt;| f   fo   /f |&lt;0.4  (1)
 
       1.02&lt; f   foLA   /f   foSM &lt;2.50  (2)

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 15/092,798 filed on Apr. 7, 2016, which is a continuation ofPCT/JP2015/059059 filed on Mar. 25, 2015 which is based upon and claimsthe benefit of priority from Japanese Patent Application No. 2015-005144filed on Jan. 14, 2015; the entire contents of which are incorporatedherein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a plurality of imaging optical systems,and in particular, to a plurality of imaging optical systems where someof the lens units in each imaging optical system are let to be common inthe plurality of imaging optical systems. Moreover, the presentinvention relates to an image pickup apparatus that includes theplurality of imaging optical systems.

Description of the Related Art

In recent years, imaging optical systems of various specifications havebeen developed. Particularly, in an interchangeable lens camera, theimaging optical system can be changed in accordance with a scene.Therefore, a user is capable of capturing various scenes. An increase inoptions of the imaging optical system can be said to be a favorablesituation for the user.

On the other hand, with an increase in types of the imaging opticalsystems, the number of components in the imaging optical system has alsoincreased. Therefore, a period of time and a cost necessary for thedevelopment of the imaging optical system, and moreover, the number ofmanufacturing lines and a production equipment cost have also increased.In such manner, the increase in the types of the imaging optical systemshas led to an increase in a burden on a manufacturer.

To solve such problems, a technology of using optical systems in commonhas been invented. A technology in which, commonality of components inimaging optical systems having different specifications is contemplated,has been proposed in Japanese Patent Application Laid-open PublicationNos. Hei 7-199067, 2010-191211, and 2006-126806.

SUMMARY OF THE INVENTION

A plurality of imaging optical systems according to an aspect of thepresent invention comprises,

at least two imaging optical systems having different focal lengths,wherein

each imaging optical system in the plurality of imaging optical systemscomprises in order from an object side,

a front lens unit having a positive refractive power,

a diaphragm member,

a focusing lens unit having a negative refractive power, and

a rear lens unit, and

the front lens unit includes one of a positive lens and a negative lensas a common lens, and

each of at least two imaging optical systems from among the plurality ofimaging optical systems includes at least one common lens, and

at the time of focusing, only the focusing lens unit moves on an opticalaxis, and

each imaging optical system satisfied the following conditionalexpression (1), and

the plurality of imaging optical systems satisfies the followingconditional expression (2):

0.06<|f _(fo) /f|<0.4  (1)

1.02<f _(foLA) /f _(foSM)<2.50  (2)

where,

f_(fo) denotes a focal length of the focusing lens unit in each imagingoptical system,

f denotes a focal length of an overall system of each imaging opticalsystem at the time of infinite object point focusing,

f_(foLA) denotes a maximum focal length from among focal lengths of thefocusing lens units in the plurality of imaging optical systems, and

f_(foSM) denotes a minimum focal length from among focal lengths of thefocusing lens units in the plurality of imaging optical systems, andhere,

the maximum focal length and the minimum focal length are to be obtainedby comparing absolute values of the focal lengths.

Moreover, a plurality of imaging optical systems according to anotheraspect of the present invention comprises,

at least two imaging optical systems having different focal lengths,wherein

each imaging optical system in the plurality of imaging optical systemscomprises in order from an object side,

a front lens unit having a positive refractive power,

a diaphragm member,

a focusing lens unit having a negative refractive power, and

a rear lens unit having a positive refractive power, and

the front lens unit includes one of a positive lens and a negative lensas a common lens, and

each of at least two imaging optical systems from among the plurality ofimaging optical systems includes at least one common lens, and

at the time of focusing, only the focusing lens unit moves on an opticalaxis, and

the plurality of imaging optical systems satisfy the followingconditional expressions (2) and (3):

1.02<f _(foLA) /f _(foSM)<2.50  (2)

1≦K _(max) /K _(min)≦1.60  (3)

where,

f_(foLA) denotes a maximum focal length from among focal lengths of thefocusing lens units in the plurality of imaging optical systems,

f_(foSM) denotes a minimum focal length from among focal lengths of thefocusing lens units in the plurality of imaging optical systems, andhere,

the maximum focal length and the minimum focal length are to be obtainedby comparing absolute values of the focal lengths,

K_(max) denotes a maximum ratio from among ratios expressed by K,

K_(min) denotes a minimum ratio from among ratios expressed by K,

here,

K (unit mm) is expressed by

K=fb _(LD) /MG _(fo),

where,

fb_(LD) is expressed by

fb _(LD) =f ²/2000 mm,

where,

f denotes a focal length of an overall system of each imaging opticalsystem at the time of infinite object point focusing, and

MG_(fo) denotes a focusing sensitivity of each imaging optical system,where,

the focusing sensitivity is an amount of movement of an image plane withrespect to a unit amount of movement of the focusing lens unit at thetime of infinite object point focusing.

Moreover, an image pickup apparatus according to the present inventioncomprises

an imaging optical system, and

an image pickup element which has an image pickup surface, and whichconverts an image formed on the image pickup surface by the imagingoptical system, to an electric signal, wherein

the imaging optical system is one of the plurality of imaging opticalsystems.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view along an optical axis showing anoptical arrangement of an imaging optical system according to an exampleA at the time of focusing to an infinite object point;

FIG. 2A, FIG. 2B, FIG. 2C, FIG. 2D, FIG. 2E, FIG. 2F, FIG. 2G, and FIG.2H are aberration diagrams according to the example A at the time offocusing to an infinite object point and at the time of focusing to aclose object point;

FIG. 3 is a cross-sectional view along an optical axis showing anoptical arrangement of an imaging optical system according to an exampleB at the time of focusing to an infinite object point;

FIG. 4A, FIG. 4B, FIG. 4C, FIG. 4D, FIG. 4E, FIG. 4F, FIG. 4G, and FIG.4H are aberration diagrams according to the example B at the time offocusing to an infinite object point and at the time of focusing to aclose object point;

FIG. 5 is a cross-sectional view along an optical axis showing anoptical arrangement of an imaging optical system according to an exampleC at the time of focusing to an infinite object point;

FIG. 6A, FIG. 6B, FIG. 6C, FIG. 6D, FIG. 6E, FIG. 6F, FIG. 6G, and FIG.6H are aberration diagrams according to the example C at the time offocusing to an infinite object point and at the time of focusing to aclose object point;

FIG. 7 is a cross-sectional view of an image pickup apparatus;

FIG. 8 is a front perspective view showing an appearance of the imagepickup apparatus;

FIG. 9 is a rear perspective view of the image pickup apparatus; and

FIG. 10 is a structural block diagram of an internal circuit of mainsections of the image pickup apparatus.

DETAILED DESCRIPTION OF THE INVENTION

Examples of plurality of imaging optical systems will be described belowin detail by referring to the accompanying diagrams. However, thepresent invention is not restricted to the examples described below.Moreover, in the plurality of imaging optical systems according to theseembodiments, common use of the main components in an imaging opticalsystem by the plurality of imaging optical systems has been facilitated.Examples of main components are lenses or lens units.

A common arrangement in a plurality of imaging optical systems accordingto a first embodiment and a plurality of imaging optical systemsaccording to a second embodiment (hereinafter, ‘plurality of imagingoptical systems according to the present embodiment’) will be describedbelow.

The plurality of imaging optical systems according to the presentembodiment includes at least two imaging optical systems havingdifferent focal lengths, and as a common arrangement, each imagingoptical system in the plurality of imaging optical systems includes inorder from an object side, a front lens unit having a positiverefractive power, a diaphragm member, a focusing lens unit having anegative refractive power, and a rear lens unit, and the front lens unitincludes one of a positive lens and a negative lens as a common lens,and each of at least two imaging optical systems from among theplurality of imaging optical systems includes at least one common lens,and at the time of focusing, only the focusing lens unit moves on anoptical axis.

In the plurality of imaging optical systems according to the presentembodiment, at least some of the lenses are used in common in eachimaging optical system. By adopting such imaging optical system, in eachimaging optical system, it is possible to position the focusing lensunit at a position posterior to a position at which, a light beam isconverged. Accordingly, since it is possible to improve an imagingmagnification of the focusing lens unit, it is possible to improve afocusing sensitivity. Furthermore, making a diameter of the focusingunit small and making the focusing unit light-weight are facilitated,and also it is possible to reduce a moving distance of the focusing lensat the time of focusing.

Furthermore, by disposing the diaphragm member on the image side of thefront lens unit, it is possible to dispose an optical stop having asmall diameter at a position at which, a light beam is converged.Therefore, it is possible to carry out both of minimizing a spacenecessary for movement of the focusing lens unit and saving a space fordisposing a drive unit. The drive unit is at least one of a first driveactuator and a second drive actuator.

The diaphragm member includes at least three components. The threecomponents are, a member determining a diaphragm diameter, a diaphragmblade member, and the first drive actuator. The first drive actuator isused for drive of a diaphragm. Moreover, an aperture stop is either themember determining the diaphragm diameter or the diaphragm blade member.Moreover, for movement of the focusing unit, the second drive actuatoris used.

When each imaging optical system is to be divided into two lens unit, itcan be divided into a front lens unit and an image-side lens unit. Theimage-side lens unit includes a diaphragm member, a focusing lens unithaving a negative refractive power, and a rear lens unit.

For shortening an overall length of the optical system, it is desirableto make the positive refractive power of the front lens unit large andto dispose a lens unit having a negative refractive power in theimage-side lens unit. By doing so, since an arrangement of the opticalsystem becomes an arrangement of a telephoto type, it is possible toachieve an effect emanated from the arrangement of the telephoto type,or in other words, to enhance an effect of shortening the overall lengthof the optical system. For such reasons, the focusing lens unit has beendisposed in the image-side lens unit.

Moreover, by guiding convergent light of the front lens unit to theimage-side lens unit having an aperture stop, particularly in theimage-side lens unit, it is possible to make small a diameter of a lenspositioned on the image side of the aperture stop. Moreover, bydisposing the focusing lens unit on the image side of the aperture stop,it becomes possible to make a member including a drive mechanism of thefocusing lens small-sized and light-weight.

Moreover, by making the refractive power of the focusing lens unitlarge, an effect emanated from the arrangement of telephoto type isenhanced. Accordingly, since the imaging magnification of the focusinglens unit is improved, it is possible to improve the focusingsensitivity. It is easily possible, as the focusing lens unit is in theimage-side lens unit of which, the diameter can be made small.Accordingly, since it is possible to make the focusing lens unitlight-weight, and to shorten the moving distance of the focusing lensunit at the time of focusing, it is possible to carry out focusing at ahigh speed.

Moreover, in the front lens unit, there is no lens that is involved infocusing. Therefore, even when the refractive power of the front lensunit is made large, by enhancing an aberration correction effect of eachlens in the front lens unit, it is possible to correct favorably aspherical aberration, a coma, an astigmatism, and a longitudinalchromatic aberration (hereinafter, ‘aberrations such as the sphericalaberration’) in the front lens unit.

Moreover, as there is no lens that is involved in focusing in the frontlens unit, it is possible to reduce an involvement of the image-sidelens unit in correction of aberrations such as the spherical aberration.In this case, since it is possible to make the refractive power of thefocusing lens unit large while a favorable imaging performance ismaintained, it is possible to enhance the effect emanated from thearrangement of the telephoto type.

Moreover, by enhancing this effect, there is a scope for a correctioncapacity with respect to aberrations such as the spherical aberration,in the front lens unit while making the front lens unit small-sized. Inan optical system that includes a telephoto system, aberrations such asthe spherical aberration are involved in a major imaging performance ofthe optical system. By letting the front lens unit have a scope withregard to the correction capacity with respect to aberrations such asthe spherical aberration, using a positive lens or a negative lenshaving a correction effect with respect to aberrations such as thespherical aberration, in common in the plurality of imaging opticalsystems, becomes easy from a design point of view. Furthermore, by ausing a lens commonly, since it is possible to use jigs and tools usedfor processing a lens at the time of manufacturing each imaging opticalsystem, making each imaging optical system low-cost is facilitated.

The plurality of imaging optical systems according to the firstembodiment will be described below. The plurality of imaging opticalsystems of the first embodiment has the aforementioned commonarrangement, and each imaging optical system satisfies the followingconditional expression (1), and the plurality of imaging optical systemssatisfies the following conditional expression (2):

0.06<|f _(fo) /f|<0.4  (1)

1.02<f _(foLA) /f _(foSM)<2.50  (2)

where,

f_(fo) denotes a focal length of the focusing lens unit in each imagingoptical system,

f denotes a focal length of an overall system of each imaging opticalsystem at the time of infinite object point focusing,

f_(foLA) denotes a maximum focal length from among focal lengths of thefocusing lens units in the plurality of imaging optical systems, and

f_(foSM) denotes a minimum focal length from among focal lengths of thefocusing lens units in the plurality of imaging optical systems, andhere,

the maximum focal length and the minimum focal length are to be obtainedby comparing absolute values of the focal lengths.

Conditional expression (1) is a conditional expression in which, therefractive power of the focusing lens unit in each imaging opticalsystem is regulated. In conditional expression (1), normalization iscarried out by the focal length of the overall system in each imagingoptical system.

When falling below a lower limit value of conditional expression (1), itis advantageous for shortening the overall length of the optical system,but a proportion of refractive power of the front lens unit increases.Since the front lens unit is a lens unit having a large aperture, aweight of the front lens unit increases. As a result, it becomesdifficult to make the overall weight light.

When exceeding an upper limit value of conditional expression (1), sincea proportion of the refractive power of the rear lens unit increases,shortening the overall length of the optical system becomes difficult.

Conditional expression (2) is a conditional expression in which, aproportion of the maximum value of the focal length of the focusing lensunit in the plurality of imaging optical systems and the minimum valueof the focal length of the focusing lens unit in the plurality ofimaging optical systems is regulated.

When falling below a lower limit value of conditional expression (2), adifference in focal lengths of overall systems of an imaging opticalsystem with the longest focal length of the focusing lens unit and animaging optical system having the minimum value with the shortest focallength of the focusing lens unit cannot be increased. Therefore, aneffective difference in specifications as an imaging optical system isnot achieved. Particularly, it becomes difficult to make an opticalsystem small-sized upon reducing an aberration fluctuation at the timeof focusing, with the spherical aberration and a curvature of fieldmaintained favorably in each imaging optical system, while letting tohave an effective difference in specifications as an imaging opticalsystem.

Moreover, when exceeding an upper limit value of conditional expression(2), a diameter of the focusing lens unit differs substantially in eachimaging optical system. In other words, a difference in a diameter ofthe focusing lens unit for an imaging optical system with the largestdiameter of the focusing lens unit and a diameter of the focusing lensunit for an imaging optical system with the smallest diameter of thefocusing lens unit becomes excessively large. In this case, since alocation for disposing a drive unit, and a space for disposing the driveunit vary for each imaging optical system, it becomes difficult to makethe diaphragm member in common.

By the difference in the diameters of the focusing lens units becominglarge, there arises a need to shift the diaphragm member in an opticalaxial direction, to set an F-number of the imaging optical system to adesired value. As aforementioned, the diaphragm member has been disposednear the focusing lens unit. Moreover, other lens or a frame member of alens is anterior and posterior to the diaphragm member. In a case inwhich, a sufficient space has been secured anterior and posterior to thediaphragm member, no problem arises for the movement of the diaphragmmember. However, in an optical system intended to be small-sized, aspace that can be secured anterior and posterior to the diaphragm memberis limited. For this reason, to avoid an interference with a lens or aframe member, there is a need to modify the diaphragm member.

Particularly, in a drive of the diaphragm member by the first driveactuator, a space in the optical axial direction is used widely. Whenthe space in the optical axial direction is widened, a lens or a framemember becomes susceptible to interfere with the diaphragm member, inthe optical axial direction. Therefore, a modification of the actuatoritself, or a modification of an actuator position in the diaphragmmember becomes necessary. Therefore, it becomes difficult to make thediaphragm member in common. For such reason, it is preferable thatconditional expression (2) is satisfied.

It is preferable that the following conditional expression (1)′ issatisfied instead of conditional expression (1).

0.1<|f _(fo) /f|<0.3  (1)′

Moreover, it is more preferable that the following conditionalexpression (1)″ is satisfied instead of conditional expression (1).

0.1<|f _(fo) /f|<0.25  (1)″

It is preferable that the following conditional expression (2)′ issatisfied instead of conditional expression (2).

1.03<f _(foLA) /f _(foSM)<2.00  (2)′

Moreover, it is more preferable that the following conditionalexpression (2)″ is satisfied instead of conditional expression (2).

1.04<f _(foLA) /f _(foSM)<1.50  (2)″

The plurality of imaging optical systems according to the secondembodiment has the aforementioned common arrangement, and the rear lensunit has a positive refractive power, and the plurality of imagingoptical systems satisfies the following conditional expressions (2) and(3).

1.02<f _(foLA) /f _(foSM)<2.50  (2)

1≦K _(max) /K _(min)≦1.60  (3)

where,

f_(foLA) denotes a maximum focal length from among focal lengths of thefocusing lens units in the plurality of imaging optical systems,

f_(foSM) denotes a minimum focal length from among focal lengths of thefocusing lens units in the plurality of imaging optical systems, andhere,

the maximum focal length and the minimum focal length are to be obtainedby comparing absolute values of the focal lengths,

K_(max) denotes a maximum ratio from among ratios expressed by K,

K_(min) denotes a minimum ratio from among ratios expressed by K,

here,

K (unit mm) is expressed by

K=fb _(LD) /MG _(fo),

where,

fb_(LD) is expressed by

fb _(LD) =f ²/2000 mm,

where

f denotes a focal length of an overall system of each imaging opticalsystem at the time of infinite object point focusing, and

MG_(fo) denotes a focusing sensitivity of each imaging optical system,where,

the focusing sensitivity is an amount of movement of an image plane withrespect to a unit amount of movement of the focusing lens unit at thetime of infinite object point focusing.

Since the technical significance of conditional expression (2) hasalready been explained, the description thereof is omitted here.

Conditional expression (3) is a conditional expression in which, aproportion of the maximum value of drive amount in the focusing lensunit and the minimum value of drive amount in the focusing lens unit isregulated. It is possible to calculate the drive amount from an amountof movement of the focusing lens unit.

At the time of focusing, the focusing lens unit and the image plane movesame direction. Therefore, numerical value of the focusing sensitivitybecomes positive value.

When exceeding an upper limit value of conditional expression (3), ineach imaging optical system of the plurality of imaging optical systemsthat uses lenses in common, it becomes difficult to carry out both ofminimizing the space necessary for the movement of the focusing lensunit and saving the space for disposing the drive unit. As a result,small-sizing of the optical system becomes difficult.

It is preferable that the following conditional expression (3)′ issatisfied instead of conditional expression (3).

1≦K _(max) /K _(min)≦1.50  (3)′

It is more preferable that the following conditional expression (3)″ issatisfied instead of conditional expression (3).

1≦K _(max) /K _(min)≦1.30  (3)″

Moreover, in the plurality of imaging optical systems according to thepresent embodiment, it is preferable that each imaging optical systemsatisfies the following conditional expression (4):

0.5<f _(ff) /f _(fb)<1.8  (4)

where,

f_(ff) denotes a focal length of the front lens unit in each imagingoptical system, and

f_(fb) denotes a focal length of the rear lens unit in each imagingoptical system.

Conditional expression (4) is a conditional expression regarding abalance of the refractive power of the front lens unit and therefractive power of the rear lens unit in each imaging optical system.

When exceeding an upper limit value of conditional expression (4), sincethe refractive power of the front lens unit becomes small, shorteningthe overall length of the optical system becomes difficult, and thefocusing sensitivity is degraded. By the focusing sensitivity beingdegraded, since the amount of movement of the focusing lens unitincreases, it becomes difficult to secure sufficiently the space for thefocusing lens unit. Moreover, the spherical aberration and the curvatureof field cannot be corrected favorably.

When falling below a lower limit value of conditional expression (4),since the refractive power of the front lens unit becomes large, thespherical aberration and the curvature of field cannot be correctedfavorably.

It is more preferable that the following conditional expression (4)′ issatisfied instead of conditional expression (4).

0.60<f _(ff) /f _(fb)<1.75  (4)′

Moreover, it is even more preferable that the following conditionalexpression (4)″ is satisfied instead of conditional expression (4).

0.65<f _(ff) /f _(fb)<1.65  (4)″

Moreover, in the plurality of imaging optical systems according to thesecond embodiment, it is preferable that each imaging optical systemsatisfies the following conditional expression (1):

0.06<|f _(fo) /f|<0.4  (1)

where,

f_(fo) denotes a focal length of the focusing lens unit in each imagingoptical system, and

f denotes a focal length of an overall system of each imaging opticalsystem at the time of infinite object point focusing.

Since the technical significance of conditional expression has alreadybeen explained, the description thereof is omitted here.

Moreover, in the plurality of imaging optical systems according to thefirst embodiment, it is preferable that the plurality of imaging opticalsystems satisfies the following conditional expression (3):

1≦K _(max) /K _(min)≦1.60  (3)

where,

K_(max) denotes a maximum ratio from among ratios expressed by K,

K_(min) denotes a minimum ratio from among ratios expressed by K,

here,

K (unit mm) is expressed by

K=fb _(LD) /MG _(fo),

where,

fb_(LD) is expressed by

fb _(LD) =f ²/2000 mm,

where,

f denotes the focal length of an overall system of each imaging opticalsystem at the time of infinite object point focusing, and

MG_(fo) denotes a focusing sensitivity of each imaging optical system,where,

the focusing sensitivity is an amount of movement of an image plane withrespect to a unit amount of movement of the focusing lens unit at thetime of infinite object point focusing.

Since the technical significance of conditional expression (3) hasalready been explained, the description thereof is omitted here.

Moreover, in the plurality of imaging optical systems according to thepresent embodiment, it is preferable that each imaging optical systemsatisfies the following conditional expression (5):

1.0<Φ_(LD)/Φ_(c)<1.25  (5)

where,

Φ_(LD) denotes a maximum effective aperture in the focusing lens unit ineach imaging optical system, and

Φ_(c) denotes a maximum diameter of an axial image forming light beam inthe focusing lens unit in each imaging optical system.

Conditional expression (5) is a conditional expression in which, aproportion of the effective aperture of the focusing lens unit in eachimaging optical system and the diameter of the image forming light beamon the optical axis is regulated.

When falling below a lower limit value of conditional expression (5),the F-number is determined by the focusing lens unit. In this case, theF-number changes with the movement of the focusing lens, and an amountof change in the F-number becomes large. When exceeding an upper limitvalue of conditional expression (5), since the effective aperture of thefocusing lens unit becomes excessively large, making the diameter of theoptical system small becomes difficult.

It is more preferable that the following conditional expression (5)′ issatisfied instead of conditional expression (5).

1.03<Φ_(LD)/Φ_(c)<1.20  (5)′

Moreover, it is even more preferable that the following conditionalexpression (5)″ is satisfied instead of conditional expression (5).

1.04<Φ_(LD)/Φ_(c)<1.15  (5)″

Moreover, in the plurality of imaging optical systems according to thepresent embodiment, it is preferable that the following conditionalexpression (6) is satisfied:

1≦LDW _(max) /LDW _(min)≦1.65  (6)

where,

LDW_(max) denotes a maximum lens gross weight from among lens grossweights of the focusing lens units in the plurality of imaging opticalsystems, and

LDW_(min) denotes a minimum lens gross weight from among lens grossweights of the focusing lens units in the plurality of imaging opticalsystems.

Conditional expression (6) is a conditional expression regarding thegross weight of the focusing lens unit in the plurality of imagingoptical systems, and is a conditional expression in which, a proportionof the maximum value of the gross weight and the minimum value of thegross weight is regulated.

When exceeding an upper limit value of conditional expression (6), in acase of using the second drive actuator in common, a degradation offocusing drive speed becomes substantial in the imaging optical systemin which, the gross weight of the focusing lens unit is the maximum.Therefore, it is not preferable to exceed the upper limit of conditionalexpression (6).

It is more preferable that the following conditional expression (6)′ issatisfied instead of conditional expression (6).

1≦LDW _(max) /LDW _(min)≦1.50  (6)′

Moreover, it is even more preferable that the following conditionalexpression (6)″ is satisfied instead of conditional expression (6).

1≦LDW _(max) /LDW _(min)≦1.40  (6)″

Moreover, in the plurality of imaging optical systems according to thepresent embodiment, it is preferable that each imaging optical systemsatisfies the following conditional expression (7):

−2<f _(fo) /f _(fb)<−0.27  (7)

where,

f_(fo) denotes a focal length of the focusing lens unit in each imagingoptical system, and

f_(fb) denotes a focal length of the rear lens unit in each imagingoptical system.

Conditional expression (7) is a conditional expression in which, aproportion of the focal lengths of the focusing lens unit and the focallengths of the rear lens units in the focusing lens units is regulated,and is a conditional expression in which, a balance of aberration andthe refractive power borne by the rear lens unit in particular, has beentaken into consideration.

When falling below a lower limit value of conditional expression (7),the focusing sensitivity becomes excessively weak. In this case, since aspace in which the focusing lens unit is to be disposed increases,small-sizing of the optical system becomes difficult. Moreover, whenexceeding an upper limit value of conditional expression (7), since itis not possible to achieve sufficiently an aberration correction effectof the rear lens unit, the spherical aberration and the curvature offield in particular, are deteriorated.

It is more preferable that the following conditional expression (7)′ issatisfied instead of conditional expression (7).

−1.7<f _(fo) /f _(fb)<−0.3  (7)′

Moreover, it is even more preferable that the following conditionalexpression (7)″ is satisfied instead of conditional expression (7).

−1.5<f _(fo) /f _(fb)<−0.3  (7)″

Moreover, in the plurality of imaging optical systems according to thepresent embodiment, it is preferable that each imaging optical systemhas an identical diaphragm member, and the following conditionalexpression (8) is satisfied:

1≦APΦ _(max) /APΦ _(min)≦1.15  (8)

where,

APΦ_(max) denotes a maximum diameter from among diameters of aperturestops in the plurality of imaging optical systems, and

APΦ_(min) denotes a minimum diameter from among diameters of aperturestops in the plurality of imaging optical systems.

It is preferable to use an identical component for the diaphragm memberin each imaging optical system. By doing so, it is possible to make theimaging magnification of the focusing lens unit large. As a result, itis possible to improve the focusing sensitivity as well as to facilitatemaking the diameter of the focusing lens unit small. Moreover, makingthe focusing lens unit light-weight is facilitated, and also it ispossible to reduce the moving distance of the focusing lens unit at thetime of focusing.

Furthermore, by disposing the diaphragm member near the focusing lensunit, not only that it is possible to dispose a small-sized diaphragmmember, but also it is possible to make a diameter of the diaphragmsmall. Accordingly, it is possible to dispose the focusing lens unit andthe drive unit while saving the space. As a result, for the plurality ofimaging optical systems, it is possible to realize easily an arrangementin which, the diaphragm member is used in common.

Conditional expression (8) is a conditional expression in which, aproportion of the maximum value of a diameter of an aperture stop in theplurality of imaging optical systems and the minimum value of a diameterof an aperture stop in the plurality of imaging optical systems isregulated. When exceeding an upper limit value of conditional expression(8), a shape of an opening in a state of maximum aperture becomes apolygonal shape in at least one imaging optical system. When the shapeof the opening is a polygonal shape, effect of blur of background isdeteriorated. Therefore, falling below the lower limit value ofconditional expression (8) or exceeding the upper limit value ofconditional expression (8) is not preferable.

Moreover, in the plurality of imaging optical system according to thepresent embodiment, it is preferable that a positive lens among thecommon lenses satisfies the following conditional expression (9):

80<νd _(P)  (9)

where,

νd_(P) denotes Abbe's number for the positive lens among the commonlenses.

In the plurality of imaging optical systems, it is preferable to have apositive lens or a negative lens as the common lens.

By satisfying conditional expression (9), in a common design of eachimaging optical system, it is possible to secure a favorable chromaticaberration. In a case in which, the positive lenses are in plurality, itis preferable that one of the positive lenses satisfies conditionalexpression (9).

Moreover, in the plurality of imaging optical systems according to thepresent embodiment, it is preferable that each imaging optical systemsatisfies the following conditional expression (10):

0.023≦SC/L≦0.110  (10)

where,

SC denotes a distance from the diaphragm member in each imaging opticalsystem up to a lens surface positioned on the object side of thefocusing lens unit, and is a distance at the time of infinite objectpoint focusing, and

L denotes a total length of the optical system in each imaging opticalsystem.

Conditional expression (10) is a conditional expression in which, alength from the diaphragm member up to a lens surface positioned on theobject side, of the focusing lens has been regulated. In conditionalexpression (10), normalization is carried out by the overall length ofthe optical system. Moreover, a basis on the diaphragm member side forcalculating SC becomes a member that determines the F-number from amongmembers included in the diaphragm member.

When falling below a lower limit value of conditional expression (10), asufficient convergence effect of converging a light beam by therefractive power of a lens unit positioned on the object side of thediaphragm (diaphragm member) cannot be achieved. Therefore, the diameterof the focusing lens unit becomes large. When exceeding an upper limitvalue of conditional expression (10), making the diameter of thefocusing lens unit small becomes easy but, shortening the overall lengthof the optical system becomes difficult.

It is more preferable that the following conditional expression (10)′ issatisfied instead of conditional expression (10).

0.025≦SC/L≦0.100  (10)′

Moreover, it is even more preferable that the following conditionalexpression (10)″ is satisfied instead of conditional expression (10).

0.040≦SC/L≦0.090  (10)″

Moreover, in the plurality of imaging optical systems according to thepresent embodiment, it is preferable that two imaging optical systemsfrom among the plurality of imaging optical systems satisfy thefollowing conditional expression (11).

1.2<f _(L) /f _(S)  (11)

where,

f_(L) denotes a long focal length from among focal lengths at the timeof infinite object point focusing of the overall system of the twoimaging optical systems, and

f_(S) denotes a short focal length from among focal lengths at the timeof infinite object point focusing of the overall system of the twoimaging optical systems.

Conditional expression (11) is a conditional expression in which, aproportion of focal lengths in two arbitrary imaging optical systemsfrom among the plurality of imaging optical systems is regulated.

When falling below a lower limit value of conditional expression (11),it is not possible to achieve effective specifications in each of thetwo imaging optical systems.

Moreover, in the plurality of imaging optical systems according to thepresent embodiment, it is preferable that a diameter of an aperture stopof the diaphragm member in each imaging optical system is let to beAPΦ_(max),

where,

APΦ_(max) denotes the maximum diameter from among the diameters of theaperture stops in the plurality of imaging optical systems.

While using the diaphragm member commonly in the plurality of imagingoptical systems, the diameter of the aperture stop in each imagingoptical system is let to be a diameter that is the maximum among thediameters of the aperture stops in the plurality of imaging opticalsystems. Moreover, for an imaging optical system that needs openingdiameter smaller than APΦ_(max), an opening member having an openingdiameter smaller than APΦ_(max) is used. In this case, it is preferableto use a member such as a diaphragm blade as an opening member, and torealize opening diameter smaller than APΦ_(max) by narrowing the openingdiameter by the member such as the diaphragm blade, for example. Bydoing so, it is possible to arrange the diaphragm member efficiently. Ina case of using two opening members, a combination of a fixed openingand a variable opening and a combination of two variable openings arepresumable.

Moreover, in the plurality of imaging optical systems according to thepresent embodiment, it is preferable that in an imaging optical systemwith an optical diaphragm diameter smaller than APΦ_(max) of thediaphragm member, setting of the optical diaphragm is carried out bydiaphragm blades narrowed down to an F-number at maximum aperture, andthe number of diaphragm blades is an odd number not less than seven.

By letting the number of diaphragm blades to be not less than seven, itis possible to form a shape of the opening at maximum aperture by thediaphragm blades to be close to a perfect circular shape. Moreover, byletting the number of diaphragm blades to be an odd number not less thanseven, it is possible to reduce diffraction intensity due to the shapeof the opening.

Moreover, in the plurality of imaging optical systems according to thepresent embodiment, it is preferable that in the imaging optical systemwith an optical diaphragm diameter smaller than APΦ_(max) of anidentical diaphragm member, a light shielding member having a circularopening section is disposed additionally near a diaphragm frame membersuch that, an F-number at maximum aperture becomes a predeterminedF-number.

By adopting such arrangement, it is possible to let a shape of theopening at maximum aperture closer to be perfect circular shaped.

Moreover, an image pickup apparatus according to the present embodimentincludes an imaging optical system, and an image pickup element whichhas an image pickup surface, and which converts an image formed on theimage pickup surface by the imaging optical system, to an electricsignal, and the imaging optical system is one of the plurality ofimaging optical systems described heretofore.

According to the image pickup apparatus of the present embodiment, sinceit is possible to use the plurality of imaging optical systems accordingto the present embodiment, it is possible to capture images of variousobjects while being small-sized and light-weight.

The abovementioned arrangements satisfy the plurality of arrangementssimultaneously. This is preferable for achieving a favorable pluralityof imaging optical systems. Moreover, combinations of preferablearrangements are arbitrary. For each conditional expression, only anupper limit value and a lower limit value of a numerical range of aconditional expression further restricted, may be restricted.

Examples of the plurality of imaging optical systems according to thepresent embodiments will be described below in detail by referring tothe accompanying diagrams. However, the present invention is notrestricted to the examples described below.

Moreover, for cutting unnecessary light such as ghost and flare, a flareaperture may be disposed apart from the aperture stop. The flareaperture may be disposed at any of locations namely, on the object sideof the front lens unit, between the front lens unit and the focusinglens unit, between the focusing lens unit and the rear lens unit, andbetween the rear lens unit and the image plane.

An arrangement may be made such that a frame member is used as a lightshielding portion of the flare aperture, or some other member may beused as the light shielding portion. Moreover, the light shieldingportion may be printed directly on the optical system, or may be painteddirectly on the optical system. Moreover, a seal etc. may be stuckdirectly on the optical system as the light shielding portion.

A shape of the shielding portion may be any shape such as a circularshape, an elliptical shape, a rectangular shape, a polygonal shape, anda range surrounded by a function curve. Not only unnecessary light beambut also a light beam such as coma flare around a screen may be cut.

The ghost and the flare may be reduced by applying an antireflectioncoating on each lens. A multilayer coating is desirable as it enables toreduce the ghost and the flare effectively. Moreover, infrared-cuttingcoating may be applied to lens surfaces and the cover glass.

For preventing the occurrence of the ghost and the flare, generally, theantireflection coating is applied to a surface of a lens in contact withair. On the other hand, at a cemented surface of a cemented lens, arefractive index of an adhesive is sufficiently higher than a refractiveindex of air. Therefore, in many cases, a reflectance is originally ofthe level of a single-layer coating or lower. Therefore, coating isapplied to a cemented surface of a cemented lens only in few cases.However, when the antireflection coating is applied positively even tothe cemented surface, it is possible to reduce further the ghost and theflare. Therefore, it is possible to achieve a more favorable image.

Particularly, recently, a glass material having a high refractive indexhas been used widely. The glass material having a high refractive index,being highly effective in aberration correction, has been used widely inan optical system of cameras. However, when the glass material having ahigh refractive index is used as a cemented lens, even a reflection atthe cemented surface becomes unignorable. In such a case, applying theantireflection coating on the cemented surface is particularlyeffective.

An effective usage of the cemented-surface coating has been disclosed inJapanese Patent Application Laid-open Publication Nos. Hei 2-27301, No.2001-324676, No. 2005-92115, and U.S. Pat. No. 7,116,482.

In these patent literatures, a cemented lens surface coating in a firstlens unit of a positive-lead zoom lens in particular, has beendescribed. It is preferable to apply the cemented surface coating to thecemented lens surface in the front lens unit having a positiverefractive power as it has been disclosed in these patent literatures.

As a coating material to be used, according to a refractive index of theadhesive material and a refractive index of the lens which is abase,coating materials such as Ta₂O₅, TiO₂, Nb₂O₅, ZrO₂, HfO₂, CeO₂, SnO₂,In₂O₃, ZnO, and Y₂O₃ having a comparatively higher refractive index, andcoating materials such as MgF₂, SiO₂, and Al₂O₃ having a comparativelylower refractive index may be selected appropriately, and set to a filmthickness that satisfies phase conditions.

Naturally, similar to the coating on the surface of the lens in contactwith air, the coating on the cemented surface may also be let to be amultilayer coating. By combining appropriately a film thickness and acoating material of number of films not less than in two layers, it ispossible to reduce further the reflectance, and to control spectralcharacteristics and angular characteristics of reflectance. Moreover, itis needless to mention that for the cemented surface of lenses otherthan the lenses in the front lens unit, it is effective to apply thecoating on the cemented surface based on a similar idea.

A plurality of imaging optical systems according to an example 1includes an imaging optical system according to an example A, an imagingoptical system according to an example B, and an imaging optical systemaccording to an example C.

A plurality of imaging optical systems according to an example 2includes the imaging optical system according to the example B and theimaging optical system according to the example B.

The imaging optical system according to the example A will be describedbelow. FIG. 1 is a cross-sectional view (lens cross-sectional view)along an optical axis showing an optical arrangement at the time ofinfinite object point focusing of the imaging optical system accordingto the example A. In all of the example A, the example B, and theexample C, a front lens unit is denoted by GF, a focusing lens unit isdenoted by Fo, a rear lens unit is denoted by GR, an aperture stop isdenoted by S, and an image plane (image pickup surface) is denoted by I.

FIG. 2A, FIG. 2B, FIG. 2C, FIG. 2D, FIG. 2E, FIG. 2F, FIG. 2G, and FIG.2H are aberration diagrams of the imaging optical system according tothe example A. Here, FIY denotes an image height. Reference numerals inaberration diagrams are same in the example B and the example C thatwill be described later.

Moreover, in these aberration diagrams, FIG. 2A, FIG. 4A, and FIG. 6Ashow a spherical aberration (SA) at the time of infinite object pointfocusing, FIG. 2B, FIG. 4B, and FIG. 6B show an astigmatism (AS) at thetime of infinite object point focusing, FIG. 2C, FIG. 4C, and FIG. 6Cshow a distortion (DT) at the time of infinite object point focusing,and FIG. 2D, FIG. 4D, and FIG. 6D show a chromatic aberration ofmagnification (CC) at the time of infinite object point focusing.

Moreover, FIG. 2E, FIG. 4E, and FIG. 6E show a spherical aberration (SA)at the time of focusing to a close object point, FIG. 2F, FIG. 4F, andFIG. 6F show an astigmatism (AS) at the time of focusing to a closeobject point, FIG. 2G, FIG. 4G, and FIG. 6G show a distortion (DT) atthe time of focusing to a close object point, and FIG. 2H, FIG. 4H, andFIG. 6H show a chromatic aberration of magnification (CC) at the time offocusing to a close object point.

The imaging optical system according to the example A, as shown in FIG.1, includes in order from an object side to an image side, a front lensunit GF having a positive refractive power, a focusing lens unit Fohaving a negative refractive power, and a rear lens unit GR having apositive refractive power. An aperture stop S is disposed between thefront lens unit GF and the focusing lens unit Fo.

The front lens unit GF includes a positive meniscus lens L1 having aconvex surface directed toward the object side, a biconvex positive lensL2, a biconcave negative lens L3, a negative meniscus lens L4 having aconvex surface directed toward the object side, a biconvex positive lensL5, a biconvex positive lens L6, a biconcave negative lens L7, abiconcave negative lens L8, and a biconvex positive lens L9. Here, thebiconvex positive lens L2 and the biconcave negative lens L3 arecemented. Moreover, the negative meniscus lens L4 and the biconvexpositive lens L5 are cemented. Furthermore, the biconvex positive lensL6 and the biconcave negative lens L7 are cemented. The biconcavenegative lens L8 and the biconvex positive lens L9 are cemented. Anarrangement of lenses from the positive meniscus lens L1 up to thebiconvex positive lens L5 is same as in the example B and the example C.

The focusing lens unit Fo includes a biconvex positive lens L10 and abiconcave negative lens L11.

The rear lens unit GR includes a biconcave negative lens L12, a biconvexpositive lens L13, a negative meniscus lens L14 having a convex surfacedirected toward the object side, and a biconvex positive lens L15. Here,the biconcave negative lens L12 and the biconvex positive lens L13 arecemented.

At the time of focusing, the focusing lens unit Fo moves along anoptical axis. More elaborately, at the time of focusing from an objectat infinity to a close object, the focusing lens unit Fo moves towardthe image side.

The imaging optical system according to the example B will be describedbelow. FIG. 3 is a cross-sectional view along an optical axis showing anoptical arrangement at the time of infinite object point focusing of theimaging optical system according to the example B. FIG. 4A, FIG. 4B,FIG. 4C, FIG. 4D, FIG. 4E, FIG. 4F, FIG. 4G, and FIG. 4H are aberrationdiagrams at the time of infinite object point focusing of the example Band at the time of focusing to a close object point of the example B.

The imaging optical system according to the example B, as shown in FIG.3, includes in order from an object side to an image side, a front lensunit GF having a positive refractive power, a focusing lens unit Fohaving a negative refractive power, and a rear lens unit GR having apositive refractive power. An aperture stop S is disposed between thefront lens unit GF and the focusing lens unit Fo.

The front lens unit GF includes a positive meniscus lens L1 having aconvex surface directed toward the object side, a biconvex positive lensL2, a biconcave negative lens L3, a negative meniscus lens L4 having aconvex surface directed toward the object side, a biconvex positive lensL5, a biconvex positive lens L6, a biconcave negative lens L7, abiconcave negative lens L8, and a biconvex positive lens L9. Here, thebiconvex positive lens L2 and the biconcave negative lens L3 arecemented. Moreover, the negative meniscus lens L4 and the biconvexpositive lens L5 are cemented. Furthermore, the biconvex positive lensL6 and the biconcave negative lens L7 are cemented. The biconcavenegative lens L8 and the biconvex positive lens L9 are cemented.

The focusing lens unit Fo includes a positive meniscus lens L10 having aconvex surface directed toward the image side, and a biconcave negativelens L11.

The rear lens unit GR includes a negative meniscus lens L12 having aconvex surface directed toward the object side, a biconvex positive lensL13, a biconvex positive lens L14, a biconcave negative lens L15, abiconcave negative lens L16, a biconvex positive lens L17, a biconvexpositive lens L18, and a negative meniscus lens L19 having a convexsurface directed toward the image side. Here, the negative meniscus lensL12 and the biconvex positive lens L13 are cemented. Moreover, thebiconvex positive lens L14 and the biconcave negative lens L15 arecemented. Furthermore, the biconvex positive lens L18 and the negativemeniscus lens L19 are cemented.

At the time of focusing, the focusing lens unit Fo moves along theoptical axis. More elaborately, at the time of focusing from an objectat infinity to a close object, the focusing lens unit Fo moves towardthe image side.

Next, the imaging optical system according to the example C will bedescribed below. FIG. 5 is a cross-sectional view along an optical axisshowing an optical arrangement at the time of infinite object pointfocusing of the imaging optical system according to the example C. FIG.6A, FIG. 6B, FIG. 6C, FIG. 6D, FIG. 6E, FIG. 6F, FIG. 6G, and FIG. 6Hare aberration diagrams at the time of infinite object point focusing ofthe example C and at the time of focusing to a close object point of theexample C.

The imaging optical system according to the example C, as shown in FIG.5, includes in order from an object side to an image side, a front lensunit GF having a positive refractive power, a focusing lens unit Fohaving a negative refractive power, and a rear lens unit GR having apositive refractive power. An aperture stop S is disposed between thefront lens unit GF and the focusing lens unit Fo.

The front lens unit GF includes a positive meniscus lens L1 having aconvex surface directed toward the object side, a biconvex positive lensL2, a biconcave negative lens L3, a negative meniscus lens L4 having aconvex surface directed toward the object side, a biconvex positive lensL5, a biconvex positive lens L6, a biconcave negative lens L7, abiconcave negative lens L8, and a biconvex positive lens L9. Here, thebiconvex positive lens L2 and the biconcave negative lens L3 arecemented. Moreover, the negative meniscus lens L4 and the biconvexpositive lens L5 are cemented. Furthermore, the biconvex positive lensL6 and the biconcave negative lens L7 are cemented. The biconcavenegative lens L8 and the biconvex positive lens L9 are cemented. Thefront lens unit GF of the example C and the front lens unit GF of theexample B are identical.

The focusing lens unit Fo includes a biconvex positive lens L10 and abiconcave negative lens L11. Here, the biconvex positive lens L10 andthe biconcave negative lens L11 are cemented.

The rear lens unit GR includes a biconcave negative lens L12, a biconvexpositive lens L13, a positive meniscus lens L14 having a convex surfacedirected toward the image side, a biconcave negative lens L15, abiconcave negative lens L16, a biconvex positive lens L17, a negativemeniscus lens L18 having a convex surface directed toward the imageside, and a positive meniscus lens L19 having a convex surface directedtoward the object side. Here, the biconcave negative lens L12 and thebiconvex positive lens L13 are cemented. Moreover, the positive meniscuslens L14 and the biconcave negative lens L15 are cemented. Furthermore,the biconvex positive lens L17 and the negative meniscus lens L18 arecemented.

At the time of focusing, the focusing lens unit Fo moves along theoptical axis. More elaborately, at the time of focusing from an objectat infinity to a close object, the focusing lens unit Fo moves towardthe image side.

Numerical data of example A, example B and example C are shown below.Apart from symbols described above, r denotes radius of curvature ofeach lens surface, d denotes a distance between respective lenssurfaces, nd denotes a refractive index of each lens for a d-line, νddenotes an Abbe number for each lens and * denotes an aspheric surface.Further, f denotes a focal length of the entire imaging optical system,FNO. denotes an F number, w denotes a half angle of view, FB denotes aback focus. FB is a unit which is expressed upon air conversion of adistance from the lens backmost surface to a paraxial image surface.Further, “Infinite” denotes at the time focusing to an infinite objectpoint, and “close” denotes at the time of focusing to a close objectpoint. Value described on the side of “Close” denotes distance to theobject point.

Example A

Unit mm Surface data Surface no. r d nd νd Object plane ∞ ∞ 1 105.7985.500 1.48749 70.23 2 192.463 31.336 3 67.537 11.600 1.49700 81.54 4−650.917 2.000 1.73400 51.47 5 292.344 27.708 6 86.044 2.000 1.8340037.16 7 41.513 9.800 1.48749 70.23 8 −234.925 1.115 9 45.444 7.9001.49700 81.54 10 −132.611 2.000 1.80400 46.58 11 72.964 3.759 12−111.443 2.000 1.67300 38.15 13 199.859 3.500 1.84666 23.78 14 −144.42010.755 15 (Stop) ∞ Variable 16 1232.351 1.800 1.84666 23.78 17 −114.3880.100 18 −114.388 1.000 1.69680 55.53 19 29.907 Variable 20 −43.0091.000 1.63980 34.46 21 59.800 4.877 1.88300 40.76 22 −48.263 0.200 2393.666 1.200 1.75520 27.51 24 34.987 5.875 25 37.030 4.362 1.59270 35.3126 −321.365 Image plane ∞ Various data Infinite Close (1.4m) f 196.005171.872 FNO. 2.890 3.36 2ω 6.3 FB 32.764 32.764 d15 7.194 20.821 d1923.263 9.635

Example B

Unit mm Surface data Surface no. r d nd νd Object plane ∞ ∞ 1 105.7985.500 1.48749 70.23 2 192.463 31.336 3 67.537 11.600 1.49700 81.54 4−650.917 2.000 1.73400 51.47 5 292.344 27.708 6 86.044 2.000 1.8340037.16 7 41.513 9.800 1.48749 70.23 8 −234.925 1.115 9 49.500 7.9001.43875 94.93 10 −120.588 2.000 1.75500 52.32 11 85.250 3.176 12−159.120 2.000 1.80440 39.59 13 185.280 3.500 1.80810 22.76 14 −182.7612.755 15 (Stop) ∞ Variable 16 1235.721 1.800 1.84666 23.78 17 −129.2410.100 18 −129.241 1.000 1.71300 53.87 19 32.003 Variable 20 35.348 1.0001.92286 18.90 21 23.584 5.300 1.53996 59.46 22 −95.147 3.100 23 210.3593.300 1.84666 23.78 24 −34.267 0.900 1.77250 49.60 25 26.998 3.917 26−40.458 0.800 1.72916 54.68 27 52.932 3.300 28 64.666 3.850 1.7204734.71 29 −94.366 1.022 30 53.290 8.100 1.56732 42.82 31 −28.431 1.5001.92286 18.90 32 −43.962 Image plane ∞ Various data Infinite Close(1.4m) f 294.894 214.374 FNO. 4.141 4.59 2ω 4.2 FB 33.351 33.351 d1521.854 39.925 d19 22.511 4.439

Example C

Unit mm Surface data Surface no. r d nd νd Object plane ∞ ∞ 1 105.7985.500 1.48749 70.23 2 192.463 31.336 3 67.537 11.600 1.49700 81.54 4−650.917 2.000 1.73400 51.47 5 292.344 27.708 6 86.044 2.000 1.8340037.16 7 41.513 9.800 1.48749 70.23 8 −234.925 1.115 9 49.500 7.9001.43875 94.93 10 −120.588 2.000 1.75500 52.32 11 85.250 3.176 12−159.120 2.000 1.80440 39.59 13 185.280 3.500 1.80810 22.76 14 −182.76113.755 15 (Stop) ∞ Variable 16 101.605 2.200 1.69895 30.13 17 −89.3261.000 1.81600 46.62 18 34.780 Variable 19 −144.791 1.000 1.92286 18.9020 38.776 5.300 1.84666 23.78 21 −59.700 3.100 22 −328.811 3.300 1.8466623.78 23 −34.760 0.100 24 −34.760 0.900 1.77250 49.60 25 55.939 1.692 26−199.510 0.800 1.77250 49.60 27 46.239 3.000 28 51.079 12.000 1.6476933.79 29 −32.908 1.200 1.84666 23.78 30 −119.520 29.615 31 37.374 5.0001.51633 64.14 32 226.417 Image plane ∞ Various data Infinite Close(1.4m) f 392.014 345.512 FNO. 5.681 6.10 2ω 3.2 FB 32.938 32.938 d1511.280 21.348 d18 16.121 6.053

Next, values of conditional expressions (1) to (11) in each example aregiven below. ‘-’ (hyphen) indicates that there is no correspondingarrangement. Values of conditional expression (11) in example 1 areshown in Table 1, and values of conditional expression (11) in example 2are shown in Table 2.

Example 1 Example 2  (2) f_(foLA)/f_(foSM) 1.21 1.16  (3)K_(max)/K_(min) 1.40 1.12  (6) LDW_(max)/LDW_(min) 1.33 1.33  (8)APΦ_(max)/APΦ_(min) 1.01 1.00 (11) f_(L)/f_(S) Table 1 Table 2

TABLE 1 Example A Example B Example C Example A — 1.50 2.00 Example B —— 1.33 Example C — — —

TABLE 2 Example B Example C Example B — 1.33 Example C — —

Example A Example B Example C  (1) |f_(fo)/f| 0.24 0.17 0.14  (4)f_(ff)/f_(fb) 1.52 0.99 0.68  (5) Φ_(LD)/Φ_(c) 1.05 1.07 1.11  (7)f_(fo)/f_(fb) −0.62 −0.38 −0.30  (9) νd_(P) 81.54 81.54 81.54 (10) SC/L0.035 0.095 0.044 APΦ 24 24.2 24.2 f_(fo) −47.0911 −48.7731 −56.818 K7.474 9.387 10.496 f 196 294.89384 392.014

FIG. 7 is a cross-sectional view of a single-lens mirrorless camera asan electronic image pickup apparatus. In FIG. 7, a photographic opticalsystem 2 is disposed inside a lens barrel of a single-lens mirrorlesscamera 1. A mount portion 3 enables the photographic optical system 2 tobe detachable from a body of the single-lens mirrorless camera 1. As themount portion 3, a mount such as a screw-type mount and a bayonet-typemount is to be used. In this example, a bayonet-type mount is used.Moreover, an image pickup element surface 4 and a back monitor 5 aredisposed in the body of the single-lens mirrorless camera 1. As an imagepickup element, an element such as a small-size CCD (charge coupleddevice) or a CMOS (complementary metal-oxide semiconductor) is to beused.

Moreover, as the photographic optical system 2 of the single-lensmirrorless camera 1, the imaging optical system described in any one ofexample A, example B and example C is to be used.

FIG. 8 and FIG. 9 are conceptual diagrams of an arrangement of the imagepickup apparatus. FIG. 8 is a front perspective view showing anappearance of a digital camera 40 as the image pickup apparatus, andFIG. 9 is a rear perspective view of the digital camera 40. The imagingoptical system according to any one of example A, example B and exampleC is used in a photographic optical system 41 of the digital camera 40.

The digital camera 40 according to the present embodiment includes thephotographic optical system 41 which is positioned in a photographicoptical path 42, a shutter button 45, and a liquid-crystal displaymonitor 47. As the shutter button 45 disposed on an upper portion of thedigital camera 40 is pressed, in conjunction with the pressing of theshutter button 45, photography is carried out by the photographicoptical system 41 such as the imaging optical system according to theexample A. An object image which is formed by the photographic opticalsystem 41 is formed on an image pickup element (photoelectric conversionsurface) which is provided near an image forming surface. The objectimage which has been received optically by the image pickup element isdisplayed on the liquid-crystal display monitor 47 which is provided toa rear surface of the camera, as an electronic image by a processingmeans. Moreover, it is possible to record the electronic image which hasbeen photographed, in a storage means.

FIG. 10 is a structural block diagram of an internal circuit of maincomponents of the digital camera 40. In the following description, theprocessing means described above includes for instance, a CDS/ADCsection 24, a temporary storage memory 117, and an image processingsection 18, and a storage means consists of a storage medium section 19for example.

As shown in FIG. 10, the digital camera 40 includes an operating section12, a control section 13 which is connected to the operating section 12,the temporary storage memory 17 and an imaging drive circuit 16 whichare connected to a control-signal output port of the control section 13,via a bus 14 and a bus 15, the image processing section 18, the storagemedium section 19, a display section 20, and a set-information storagememory section 21.

The temporary storage memory 17, the image processing section 18, thestorage medium section 19, the display section 20, and theset-information storage memory section 21 are structured to be capableof mutually inputting and outputting data via a bus 22. Moreover, theCCD 49 and the CDS/ADC section 24 are connected to the imaging drivecircuit 16.

The operating section 12 includes various input buttons and switches,and informs the control section 13 of event information which is inputfrom outside (by a user of the digital camera) via these input buttonsand switches. The control section 13 is a central processing unit (CPU),and has a built-in computer program memory which is not shown in thediagram. The control section 13 controls the entire digital camera 40according to a computer program stored in this computer program memory.

The CCD 49 is driven and controlled by the imaging drive circuit 16, andwhich converts an amount of light for each pixel of the object imageformed by the photographic optical system 41 to an electric signal, andoutputs to the CDS/ADC section 24.

The CDS/ADC section 24 is a circuit which amplifies the electric signalwhich is input from the CCD 49, and carries out analog/digitalconversion, and outputs to the temporary storage memory 17 image rawdata (Bayer data, hereinafter called as ‘RAW data’) which is onlyamplified and converted to digital data.

The temporary storage memory 17 is a buffer which includes an SDRAM(Synchronous Dynamic Random Access Memory) for example, and is a memorydevice which stores temporarily the RAW data which is output from theCDS/ADC section 24. The image processing section 18 is a circuit whichreads the RAW data stored in the temporary storage memory 17, or the RAWdata stored in the storage medium section 19, and carries outelectrically various image-processing including the distortioncorrection, based on image-quality parameters specified by the controlsection 13.

The storage medium section 19 is a recording medium in the form of acard or a stick including a flash memory for instance, detachablymounted. The storage medium section 19 records and maintains the RAWdata transferred from the temporary storage memory 17 and image datasubjected to image processing in the image processing section 18 in thecard flash memory and the stick flash memory.

The display section 20 includes the liquid-crystal display monitor, anddisplays photographed RAW data, image data and operation menu on theliquid-crystal display monitor. The set-information storage memorysection 21 includes a ROM section in which various image qualityparameters are stored in advance, and a RAM section which stores imagequality parameters which are selected by an input operation on theoperating section 12, from among the image quality parameters which areread from the ROM section.

In the single-lens mirrorless camera 40 arranged in such manner, byusing the plurality of imaging optical systems according to the presentinvention as the photographing optical system 41, it is possible tocapture images of various objects while being small-sized andlight-weight. The plurality of imaging optical systems according to thepresent invention can be used also in an image pickup apparatus of atype having a quick-return mirror.

According to the embodiments, it is possible to provide a plurality ofimaging optical systems in which, while facilitating a common use ofmain lens components of an imaging optical system, in the plurality ofimaging optical systems, it is possible to reduce a burden ofdevelopment on manufacturer by facilitating making these main lenscomponents small-sized and light-weight, and besides to facilitatemaking a product small-sized and light-weight. Moreover, it is possibleto provide an image pickup apparatus using the plurality of imagingoptical systems.

As described heretofore, the present invention is useful in a pluralityof imaging optical systems in which, while facilitating a common use ofmain components of an imaging optical system, in the plurality ofimaging optical systems, and it is possible to reduce a burden ofdevelopment on manufacturer by facilitating making these main componentssmall-sized and light-weight, and besides to facilitate making a productsmall-sized and light-weight. Moreover, the present invention is usefulin an image pickup apparatus using the plurality of imaging opticalsystems.

What is claimed is:
 1. A plurality of imaging optical systemscomprising: at least two imaging optical systems having different focallengths, wherein each imaging optical system in the plurality of imagingoptical systems comprises in order from an object side, a front lensunit having a positive refractive power, a diaphragm member, a focusinglens unit having a negative refractive power, and a rear lens unit, andthe front lens unit includes one of a positive lens and a negative lensas a common lens, and each of at least two imaging optical systems fromamong the plurality of imaging optical systems includes at least onecommon lens, and at the time of focusing, only the focusing lens unitmoves on an optical axis, and each imaging optical system satisfies thefollowing conditional expression (1), and the plurality of imagingoptical systems satisfies the following conditional expression (2):0.06<|f _(fo) /f|<0.4  (1)1.02<f _(foLA) /f _(foSM)<2.50  (2) where, f_(fo) denotes a focal lengthof the focusing lens unit in each imaging optical system, f denotes afocal length of an overall system of each imaging optical system at thetime of infinite object point focusing, f_(foLA) denotes a maximum focallength from among focal lengths of the focusing lens units in theplurality of imaging optical systems, and f_(foSM) denotes a minimumfocal length from among focal lengths of the focusing lens units in theplurality of imaging optical systems, and here, the maximum focal lengthand the minimum focal length are to be obtained by comparing absolutevalues of the focal lengths.
 2. A plurality of imaging optical systemscomprising: at least two imaging optical systems having different focallengths, wherein each imaging optical system in the plurality of imagingoptical systems comprises in order from an object side, a front lensunit having a positive refractive power, a diaphragm member, a focusinglens unit having a negative refractive power, and a rear lens unithaving a positive refractive power, and the front lens unit includes oneof a positive lens and a negative lens as a common lens, and each of atleast two imaging optical systems from among the plurality of imagingoptical systems includes at least one common lens, and at the time offocusing, only the focusing lens unit moves on an optical axis, and theplurality of imaging optical systems satisfy the following conditionalexpressions (2) and (3):1.02<f _(foLA) /f _(foSM)<2.50  (2)1≦K _(max) /K _(min)≦1.60  (3) where, f_(foLA) denotes a maximum focallength from among focal lengths of the focusing lens units in theplurality of imaging optical systems, f_(foSM) denotes a minimum focallength from among focal lengths of the focusing lens units in theplurality of imaging optical systems, and here, the maximum focal lengthand the minimum focal length are to be obtained by comparing absolutevalues of the focal lengths, K_(max) denotes a maximum ratio from amongratios expressed by K, K_(min) denotes a minimum ratio from among ratiosexpressed by K, here, K (unit mm) is expressed byK=fb _(LD) /MG _(fo), where, fb_(LD) is expressed byfb _(LD) =f ²/2000 mm, where, f denotes a focal length of an overallsystem of each imaging optical system at the time of infinite objectpoint focusing, and MG_(fo) denotes a focusing sensitivity of eachimaging optical system, where, the focusing sensitivity is an amount ofmovement of an image plane with respect to a unit amount of movement ofthe focusing lens unit at the time of infinite object point focusing. 3.The plurality of imaging optical systems according to claim 1, whereineach imaging optical system satisfies the following conditionalexpression (4):0.5<f _(ff) /f _(fb)<1.8  (4) where, f_(ff) denotes a focal length ofthe front lens unit in each imaging optical system, and f_(fb) denotes afocal length of the rear lens unit in each imaging optical system. 4.The plurality of imaging optical systems according to claim 2, whereineach imaging optical system satisfies the following conditionalexpression (4):0.5<f _(ff) /f _(fb)<1.8  (4) where, f_(ff) denotes a focal length ofthe front lens unit in each imaging optical system, and f_(fb) denotes afocal length of the rear lens unit in each imaging optical system. 5.The plurality of imaging optical systems according to claim 2, whereineach imaging optical system satisfies the following conditionalexpression (1):0.06<|f _(fo) /f|<0.4  (1) where, f_(fo) denotes a focal length of thefocusing lens unit in each imaging optical system, and f denotes thefocal length of an overall system of each imaging optical system at thetime of infinite object point focusing.
 6. The plurality of imagingoptical systems according to claim 1, wherein the plurality of imagingoptical systems satisfies the following conditional expression (3):1≦K _(max) /K _(min)≦1.60  (3) where, K_(max) denotes a maximum ratiofrom among ratios expressed by K, K_(min) denotes a minimum ratio fromamong ratios expressed by K, here, K (unit mm) is expressed byK=fb _(LD) /MG _(fo), where, fb_(LD) is expressed byfb _(LD) =f ²/2000 mm, where, f denotes the focal length of an overallsystem of each imaging optical system at the time of infinite objectpoint focusing, and MG_(fo) denotes a focusing sensitivity of eachimaging optical system, where, the focusing sensitivity is an amount ofmovement of an image plane with respect to a unit amount of movement ofthe focusing lens unit at the time of infinite object point focusing. 7.The plurality of imaging optical systems according to claim 1, whereineach imaging optical system satisfies the following conditionalexpression (5):1.0<Φ_(LD)/Φ_(c)<1.25  (5) where, Φ_(LD) denotes a maximum effectiveaperture in the focusing lens unit in each imaging optical system, andΦ_(c) denotes a maximum diameter of an axial image forming light beam inthe focusing lens unit in each imaging optical system.
 8. The pluralityof imaging optical systems according to claim 2, wherein each imagingoptical system satisfies the following conditional expression (5):1.0<Φ_(LD)/Φ_(c)<1.25  (5) where, Φ_(LD) denotes a maximum effectiveaperture in the focusing lens unit in each imaging optical system, andΦ_(c) denotes a maximum diameter of an axial image forming light beam inthe focusing lens unit in each imaging optical system.
 9. The pluralityof imaging optical systems according to claim 1, wherein the followingconditional expression (6) is satisfied:1≦LDW _(max) /LDW _(min)≦1.65  (6) where, LDW_(max) denotes a maximumlens gross weight from among lens gross weights of the focusing lensunits in the plurality of imaging optical systems, and LDW_(min) denotesa minimum lens gross weight from among lens gross weights of thefocusing lens units in the plurality of imaging optical systems.
 10. Theplurality of imaging optical systems according to claim 2, wherein thefollowing conditional expression (6) is satisfied:1≦LDW _(max) /LDW _(min)≦1.65  (6) where, LDW_(max) denotes a maximumlens gross weight from among lens gross weights of the focusing lensunits in the plurality of imaging optical systems, and LDW_(min) denotesa minimum lens gross weight from among lens gross weights of thefocusing lens units in the plurality of imaging optical systems.
 11. Theplurality of imaging optical systems according to claim 1, wherein eachimaging optical system satisfies the following conditional expression(7):−2<f _(fo) /f _(fb)<−0.27  (7) where, f_(fo) denotes the focal length ofthe focusing lens unit in each imaging optical system, and f_(fb)denotes a focal length of the rear lens unit in each imaging opticalsystem.
 12. The plurality of imaging optical systems according to claim2, wherein each imaging optical system satisfies the followingconditional expression (7):−2<f _(fo) /f _(fb)<−0.27  (7) where, f_(fo) denotes the focal length ofthe focusing lens unit in each imaging optical system, and f_(fb)denotes a focal length of the rear lens unit in each imaging opticalsystem.
 13. The plurality of imaging optical systems according to claim1, wherein each imaging optical system has an identical diaphragmmember, and the following conditional expression (8) is satisfied:1≦APΦ _(max) /APΦ _(min)≦1.15  (8) where, APΦ_(max) denotes a maximumdiameter from among diameters of aperture stops in the plurality ofimaging optical systems, and APΦ_(min) denotes a minimum diameter fromamong diameters of aperture stops in the plurality of imaging opticalsystems.
 14. The plurality of imaging optical systems according to claim2, wherein each imaging optical system has an identical diaphragmmember, and the following conditional expression (8) is satisfied:1≦APΦ _(max) /APΦ _(min)≦1.15  (8) where, APΦ_(max) denotes a maximumdiameter from among diameters of aperture stops in the plurality ofimaging optical systems, and APΦ_(min) denotes a minimum diameter fromamong diameters of aperture stops in the plurality of imaging opticalsystems.
 15. The plurality of imaging optical systems according to claim1, wherein a positive lens from among the common lenses satisfies thefollowing conditional expression (9):80<νd _(P)  (9) where, νd_(P) denotes Abbe's number for the positivelens from among the common lenses.
 16. The plurality of imaging opticalsystems according to claim 2, wherein a positive lens from among thecommon lenses satisfies the following conditional expression (9):80<νd _(P)  (9) where, νd_(P) denotes Abbe's number for the positivelens from among the common lenses.
 17. The plurality of imaging opticalsystems according to claim 1, wherein each imaging optical systemsatisfies the following conditional expression (10):0.023≦SC/L≦0.110  (10) where, SC denotes a distance from the diaphragmmember in each imaging optical system up to a lens surface positioned onthe object side of the focusing lens unit, and is a distance at the timeof infinite object point focusing, and L denotes a total length of theoptical system in each imaging optical system.
 18. The plurality ofimaging optical systems according to claim 2, wherein each imagingoptical system satisfies the following conditional expression (10):0.023≦SC/L≦0.110  (10) where, SC denotes a distance from the diaphragmmember in each imaging optical system up to a lens surface positioned onthe object side of the focusing lens unit, and is a distance at the timeof infinite object point focusing, and L denotes a total length of theoptical system in each imaging optical system.
 19. The plurality ofimaging optical systems according to claim 1, wherein two imagingoptical systems from among the plurality of imaging optical systemssatisfy the following conditional expression (11):1.2<f _(L) /f _(S)  (11) where, f_(L) denotes a long focal length fromamong focal lengths at the time of infinite object point focusing of theoverall system of the two imaging optical systems, and f_(S) denotes ashort focal length from among focal lengths at the time of infiniteobject point focusing of the overall system of the two imaging opticalsystems.
 20. The plurality of imaging optical systems according to claim2, wherein two imaging optical systems from among the plurality ofimaging optical systems satisfy the following conditional expression(11):1.2<f _(L) /f _(S)  (11) where, f_(L) denotes a long focal length fromamong focal lengths at the time of infinite object point focusing of theoverall system of the two imaging optical systems, and f_(S) denotes ashort focal length from among focal lengths at the time of infiniteobject point focusing of the overall system of the two imaging opticalsystems.
 21. The plurality of imaging optical systems according to claim13, wherein a diameter of an aperture stop of the diaphragm member ineach imaging optical system is let to be APΦ_(max), where, APΦ_(max)denotes the maximum diameter from among diameters of aperture stops inthe plurality of imaging optical systems.
 22. The plurality of imagingoptical systems according to claim 14, wherein a diameter of an aperturestop of the diaphragm member in each imaging optical system is let to beAPΦ_(max), where, APΦ_(max) denotes the maximum diameter from amongdiameters of aperture stops in the plurality of imaging optical systems.23. The plurality of imaging optical systems according to claim 21,wherein in an imaging optical system with an optical diaphragm diametersmaller than APΦ_(max) of the diaphragm member, setting of the opticaldiaphragm is carried by diaphragm blades narrowed down to an F-number atmaximum aperture, and the number of diaphragm blades is an odd numbernot less than seven.
 24. The plurality of imaging optical systemsaccording to claim 22, wherein in an imaging optical system with anoptical diaphragm diameter smaller than APΦ_(max) of the diaphragmmember, setting of the optical diaphragm is carried by diaphragm bladesnarrowed down to an F-number at maximum aperture, and the number ofdiaphragm blades is an odd number not less than seven.
 25. The pluralityof imaging optical systems according to claim 21, wherein in the imagingoptical system with an optical diaphragm diameter smaller than APΦ_(max)of an identical diaphragm member, a light shielding member having acircular opening section is disposed additionally near a diaphragm framemember such that, an F-number at maximum aperture becomes apredetermined F-number.
 26. The plurality of imaging optical systemsaccording to claim 22, wherein in the imaging optical system with anoptical diaphragm diameter smaller than APΦ_(max) of an identicaldiaphragm member, a light shielding member having a circular openingsection is disposed additionally near a diaphragm frame member suchthat, an F-number at maximum aperture becomes a predetermined F-number.27. An image pickup apparatus comprising: an imaging optical system; andan image pickup element which has an image pickup surface, and whichconverts an image formed on the image pickup surface by the imagingoptical system, to an electric signal, wherein the imaging opticalsystem is one of the plurality of imaging optical systems according toclaim
 1. 28. An image pickup apparatus comprising: an imaging opticalsystem; and an image pickup element which has an image pickup surface,and which converts an image formed on the image pickup surface by theimaging optical system, to an electric signal, wherein the imagingoptical system is one of the plurality of imaging optical systemsaccording to claim 2.